YoutubePeople responding to the viral #CharlieCharlieChallenge post videos of the game on social media.

A Vatican-approved exorcist has warned against the dangers of playing the game known as "Charlie, Charlie," which is gaining popularity among young people on social media.

Spanish priest Jose Antonio Fortea said the so-called Charlie Charlie Challenge, a game played on a simplified version of the Ouija board, poses a real danger as it involves the summoning of spirits, the Catholic News Agency reported on Wednesday.

The game uses two pens and a paper to create a makeshift version of the Ouija board. A grid is drawn on paper to make four panels, two of which are labelled "yes" and the other two "no." The pens are then put on top of another, positioned like a cross.

The players invoke a Mexican demon by calling out "Charlie, Charlie can we play" or "Charlie, Charlie are you here?" Then they wait for the pen to move as they film the game for online posting.

Father Fortea warned that the game involves the real, occult practice of "calling on spirits," cautioning people that "some spirits who are at the root of that practice will harass some of those who play the game."

Even though players "won't be possessed," the spirit that has been summoned "will stay around for a while."

Also, the game "will result in other spirits beginning to enter into even more frequent communication."

"And so then the person really can suffer much worse consequences from the demons," Father Fortea said.

Another priest, Fr Stephen McCarthy, warned students at the Saints John Neumann and Maria Goretti Catholic High School in Philadelphia against playing the game, The Independent reported on Tuesday.

"There is a dangerous game going around on social media which openly encourages impressionable young people to summon demons," Father McCarthy said in an open letter.

"I want to remind you all there is no such thing as 'innocently playing with demons.'"

"Please be sure to NOT participate and encourage others to avoid participation as well."

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"The problem with opening yourself up to demonic activity is that it opens a window of possibilities which is not easily closed," he said.

The origin of the fad remains unclear. Time suggested that versions of the game can be traced to 2008. A YouTube video, "Jugando Charly Charlie," was posted in June last year but the game, which uses pencils, is a little different.

Twitter user @_kluh was one of the first who adopted the hashtag #CharlieCharlieChallenge, which was used by over two million people, wrote the BBC on Monday.

Occult activity and the need for exorcisms has increased to a critical level globally, with the spokesperson for the International Association of Exorcists saying the number of bishops and cardinals asking to be part of their annual conference due to rising demonic activity has been going up.

"It's becoming a pastoral emergency," Cascioli told Catholic News Agency. "At the moment the number of disturbances of extraordinary demonic activity is on the rise."

The increase in demonic activity can be linked to dwindling faith among people and a growing interest and participation in occult activities like Ouija boards and seances, said Cascioli.